The present invention relates to an industrial vehicle on which a fuel cell system is mounted, and more particularly, to an industrial vehicle having a fuel cell system which is controlled in conjunction with the on and off operation of a key switch of the vehicle.
Vehicles having a fuel cell system have been now put into practical use. Generally, a fuel cell system having a fuel cell stack formed by laminating a plurality of power generating cells is configured to generate electric power by supplying hydrogen gas and air to the fuel cell stack and causing chemical reaction between the hydrogen gas and oxygen contained in the air in the respective power generating cells.
Examples of the practical applications of such fuel cell system include industrial vehicles such as forklift trucks. In some of the industrial vehicles having the fuel cell system, the fuel cell system is controlled in conjunction with the on and off operation of the key switch of the vehicle. Specifically, when the key switch of the industrial vehicle is turned on, the fuel cell system starts generation of electric power and the vehicle becomes operable; when the key switch is turned off, the electric power generation of the fuel cell system is stopped or suspended and the vehicle becomes inoperable. Japanese Unexamined Patent Application Publication No. 2014-50240 discloses an industrial vehicle of the type described above.
It is a usual practice for an operator of an industrial vehicle such as a forklift truck to get on and get off the vehicle frequently for the reason of various works to do on and off the vehicle. As a safety education, operators of the forklift truck are instructed to always turn the key switch of the forklift truck to the OFF position before getting off the forklift truck, regardless of whether it is a temporal leave or not. Therefore, the key switch of the industrial vehicle is turned on and off frequently and accordingly the electric power generation of the fuel cell system is started and suspended frequently in conjunction with the turning on and off operation of the key switch.
In general, frequent switching between the start and the suspension of electric power generation of the fuel cell system in a vehicle accelerates deterioration of the fuel cell stack of the fuel cell system. In particular, it is generally known that the deterioration of the fuel cell stack is accelerated if the voltage of cells of the fuel cell stack varies crossing their allowable minimum voltage of approx. 0.6 V.
In starting the fuel cell system for electric power generation, air compressor needs to be started for supplying air to the fuel cell stack. However, starting the air compressor requires a large amount of electric power. In stopping or suspending the electric power generation of the fuel cell system, the air compressor is kept running for a specified period of time in order to drain water remaining in the fuel cell stack, which also requires some electric power. In other words, repeated start and stop of electric power generation of the fuel cell system also poses a problem in the energy efficiency.
The present invention which has been made in view of the circumstances above is directed to providing an industrial vehicle having a fuel cell system that is capable of preventing deterioration of the fuel cell stack and a drop in the energy efficiency under a working environment where the key switch of the vehicle is turned on and off frequently.